PROJECT SUMMARY Up to 20% of treated women with early stage breast cancer will suffer from local recurrences on the chest wall (RCW). Treatment of local recurrences is problematic and surgery provides only a 33% 5-year control rate. Radiation therapy is a preferred option, but efficacy is low for larger lesions (>3 cm diameter) and additional rounds of radiation therapy are associated with other long-term risks due to cumulative ionizing radiation. POP Biotechnologies (POP BIO) is advancing a relatively unexplored tumor-treatment technique for RCW breast cancer: chemo-phototherapy (CPT). CPT involves the intravenous injection of long-circulating, doxorubicin- loaded, porphyrin-phospholipid (PoP) liposomes (NP-01) followed by tumor irradiation with a near infrared (NIR) laser resulting in the permeabilization of the liposomes and deposition of doxorubicin localized in the tumor. At present, few, if any, light-controlled systems can achieve robust, on-demand spatial and temporal control of nanovesicle permeabilization in biological environments. Unlike heat-triggered drug release approaches, NP-01 is fully stable in serum, yet rapidly release their contents when exposed to clinically-relevant NIR laser irradiation. In mouse models, a single mild laser treatment deposits large amounts of drug, leading to permanent tumor eradication. In this proposal, PoP Biotechnologies will develop scalable liposome formulation protocols using a lipid extrusion approach and evaluate the resulting NP-01 product. This project has two specific aims: Aim 1: Reproducibly produce and characterize doxorubicin-loaded PoP liposomes (NP-01) using a scalable approach; and Aim 2: Assess in vivo pharmacokinetics, efficacy and toxicity of NP-01 in rats. Pending a successful outcome of this Phase I grant application, we will put forward a Phase II grant application involving more in depth studies for treatment dosimetry and efficacy in large animals pertinent for translation to human trials.